This application claims the priority of Korean Patent Application No. 2001-62078, filed Oct. 9, 2001 in the Korean Intellectual Property Office, which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a micro mirror device for changing the reflection path of light by actuating a micro mirror, and a projector employing the same, and more particularly, to a micro mirror device capable of realizing color images without a color wheel by selectively reflecting color beams using a plurality of micro mirrors whose driving axes are positioned at different angles, and a projector employing the same.
2. Description of the Related Art
In general, a micro mirror device includes a plurality of micro mirrors actuated by electrostatic attraction, and changes the reflection path of light by changing the reflection angle of light according to the angle or direction of each inclined micro mirror. Such a micro mirror device can be applied to an image display of a projection television, a scanner, a copy machine or a facsimile. In particular, when used for an image display, the micro mirror device produces an image by two dimensionally arranging as many micro mirrors as the number of pixels, actuating each micro mirror individually in response to an image signal for each pixel, and determining the reflection angle of incident light.
Referring to FIG. 1, a conventional micro mirror device 115 includes a plurality of micro mirrors 100 that are arranged two dimensionally, and whose driving axes Y are positioned in the same direction. The micro mirrors 100 are actuated with regard to the driving axes Y to be switched on or off, and selectively reflect beams incident upon them.
FIG. 2 is a view of a projector employing a conventional micro mirror device as illustrated in FIG. 1. Referring to FIG. 2, a beam is emitted from a light source 120, focused by a first condenser 122, and incident upon a color wheel 125. Here, a color image is realized by rotating the color wheel 125 at high speed to sequentially illuminate beams of three colors, i.e., R(red), G(green), B(blue), on the single plate micro mirror device 115. The beam, which passed through the color wheel 125, is incident upon the micro mirror device 115 having as many micro mirrors 100 as the number of pixels via a second condenser 127. When the micro mirror device 115 is actuated in response to image signals for each pixel, each micro mirror 100 is inclined at a predetermined angle. Then color beams corresponding to pixels are reflected at proper angles, and travel toward a projection lens unit 133. Next, the beams are magnified by the projection lens unit 133, and the magnified image form on a screen 135.
Here, the micro mirror 100 is switched on or off to selectively reflect R, G, B beams which are sequentially transmitted from the color wheel 125. At this time, since the driving axes Y of the micro mirrors 100 head toward the same direction, the micro mirrors 100 are switched on or off to sequentially reflect R, G, B beams in the same direction or at the same angle.
However, because the color wheel 125 rotates at high speed, it makes noise and is not actuated stably. Further, due to the mechanical limitation of the color wheel 125, the color wheel 125 does not rotate beyond a predetermined speed, which would cause color breakup. Also, light may be lost at the filter borders of the color wheel 125, and therefore, light must be concentrated to have a very small beam size so as to prevent this problem. However, there is a limitation in reducing light to beam size. Thus it is inevitable that light escapes at the borders. In addition, the color wheel 125 is very expensive, thereby increasing manufacturing cost.